The amplitudes and frequencies of protein motions that permit molecules to approach interior trytophan residues will be investigated by using fluorescence quenchers of varying size and structure. The extent to which quenchers that are not dissolved in the protein at the time of excitation contribute to the quenching will be assessed by recording the decay profiles at short times after excitation with a pulsed laser. The effect of hydration on the mobility of proteins will be examined. A comparison of current sampling and time-correlated photon counting detection methods will be made by using two different subnanosecond laser sources.